A New Technique for In Situ Determination of the Active Surface Area Changes of Li–Ion Battery Electrodes

Abstract

Li‐ion batteries have been of a great interest for over three decades. A geometric electrode surface area is generally used for Li‐ion electrochemical parameters calculations. Since the real electrode is a complex system composed of the thick porous structure, the contact surface area between the active mass and electrolyte is far larger than geometrical. This approximation leads to a large deviation of obtained results, especially within different laboratories and for volume and surface changing materials, e. g., silicon. The article presents a new method of in situ analysis of active surface area variations applicable for Li‐ion electrodes. The method relies on the electrochemical impedance spectroscopy measurement (EIS) performed at an arbitrarily chosen state of charge during superimposed DC current flow. The correlation between a local ion concentration with a charge transfer resistance allows to evaluate the differences of the active surface area. The presented method is not affected by the SEI layer presence, the material composition, nor the lithiation mechanism. Due to limited EIS frequency range the presented method can be performed with a relatively short time. Our new in situ surface area determination can greatly improve the accuracy of the electrochemical parameters evaluation and enable the proper result analysis. We believe that our method can become a standard procedure implemented in every research focusing on the electrochemical parameter determination of the volume changing active materials.

Operando Quantified Lithium Plating Determination Enabled by Dynamic Capacitance Measurement in Working Li‐Ion Batteries

“…The η increases slightly during each plateau, indicating a rising trend of R CT . During battery charging, the volume of graphite particles keeps increasing and ECSA increases consequently [23] . Meanwhile, the increase of R CT in the plateau mainly results from the enrichment of Li + on graphite surface.…”

Engineering Prelithiation of Polyacrylic Acid Binder: A Universal Strategy to Boost Initial Coulombic Efficiency for High‐Areal‐Capacity Si‐Based Anodes

“…Two semicircles ascribe to the SEI resistance and charge transfer resistance are overlapped with each in the Nyquist plots because of the similar time constants. [ 34 ] The smaller interfacial resistance of the SiO x @Li 0.75 PAA suggests the fast electrochemical kinetics of the SiO x @Li 0.75 PAA during cycling. The slopes obtained by the impedance ( Z ′) and reciprocal square root of frequency (ω −1/2 ) fitting were used to compare the Li–ion diffusion ability of different electrodes during cycling.…”

Operando Quantified Lithium Plating Determination Enabled by Dynamic Capacitance Measurement in Working Li‐Ion Batteries

“…The surface morphology of the Gr anode exhibits no Li plating at 1900.0 s (Figure 3g), corresponding to an NI of 111.5 %. Since an 8.5 % increase in the ESCA of Gr is revealed by Ratynski and coworkers, [23] it is conservative to set 110.0 % as the NI for onset Li plating. The growth of C S values after 2500.0 s exhibits a linear trend with a larger slope compared to the results at a lower C-rate (Figure S6), which is attributed to the dendritic morphology at 1.0 C. By comparing the variation trend of C S values in Figure 3e with that of DCM tests on saturated LiC 6 (Figure S7), it can be concluded that the Li + intercalation is absent in the total current flow after 2500.0 s (the insert images in Figure 3h and l).…”